Method and Apparatus for Reducing Patterning Effects on a Substrate During Radiation-Based Heating

Abstract

Patterning effects on a substrate are reduced during radiation-based heating by filtering the radiation source or configuring the radiation source to produce radiation having different spectral characteristics. For the filtering, an optical filter may be used to truncate specific wavelengths of the radiation. The different configurations of the radiation source include a combination of one or more continuum radiation sources with one or more discrete spectrum sources, a combination of multiple discrete spectrum sources, or a combination of multiple continuum radiation sources. Furthermore, one or more of the radiation sources may be configured to have a substantially non-normal angle of incidence or polarized to reduce patterning effects on a substrate during radiation-based heating.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]Embodiments of the present invention generally relate to thermal processing of a substrate and more particularly to method and apparatus for reducing patterning effects on a substrate during radiation-based heating.[0003]1. Description of the Related Art[0004]Some methods of thermal processing of substrates, such as rapid thermal processing (RTP) or laser thermal processing (LTP), rely on radiation-based heating of substrates. For example, RTP is performed on a silicon wafer for the manufacture of integrated circuits by heating a wafer using high-output lamps, such as halogen lamps. The wafer is heated for a short time to a peak temperature, often on the order of 800 to 1000 degrees Celsius, for the formation of a layer of oxide, nitride, or silicide on the wafer, or to anneal an implanted wafer.[0005]Substrate temperatures achieved in radiation-based heating strongly depend on the amount of incident radiation absorbed ...

AI Technical Summary

Benefits of technology

[0014]In view of the above, embodiments of the present invention provide an apparatus and a method for reducing patterning effects on a substrate during radiation-based heating by filtering the radiation source or configuring the radiation source to produce radiation having different spectral characteristics. For filtering, an optical filter may be used to truncate specific wavelengths of the radiation. The different configurations of the radiation source include a combination of one or more continuum radiation sources with one or more discrete spectrum sources, a combination of multiple discrete spectrum sources, or a combination of multiple continuum radiation sources. Furthermore, one or more of the radiation sources may be configured to have a substantially non-normal angle of incidence or may be polarized to reduce patterning effects on a substrate during radiation-based heating.

Problems solved by technology

Conductive heat transfer from “hot spots” to “cold spots” on the substrate generally cannot adequately ameliorate these gradients due to the short duration of radiation-based heating processes.

Further, the spectral power distribution for this continuum radiator is not flat, i.e., more energy produced by the radiator is concentrated in certain wavelengths over other wavelengths, producing a non-uniform spectral power distribution.

Such a non-uniform spectral power distribution is typical for continuum radiators.

Thermal gradients across a device caused by patterning effects can result in non-uniform electrical properties on the device, which strongly influence the overall device performance.

In some cases, such unwanted thermal gradients may even render the device unusable or less reliable due to incomplete thermal processing in some parts of the device and over-processing in others.

In regions corresponding to “hot spots”, a device may be detrimentally affected in other ways, for example from unwanted diffusion of implanted atoms into the substrate or by exceeding the thermal budget of devices formed in that region.

While this approach may reduce temperature gradients across the substrate as a whole, temperature gradients within a single IC die caused by patterning effects will remain unaffected.

This is because the scale of intra-die temperature gradients, which is on the order of micrometers, is far too small for different configurations of lamp arrays to correct.

Moreover, modulation of the intensity of incident radiation during radiation-based heating is also unable to thermal reduce patterning effects since this method does not address the fundamentally different optical characteristics of different regions on the surface of a substrate.

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